Principles of Plant Systematics II

A Quick Review And

Some Fun!

Monophyletic Group (= Clade)

• A group composed of an ancestor and all its descendants.

Synapomorphy

• Shared derived character state.• Synapomorphies have arisen in a common

ancestor and are present in all the members of a group though sometimes in modified form.

• Synapomorphies can be morphological, chemical, genetic, behavioral, etc.

Phylogenetic Tree (= Cladogram)

What Assumptions/Problems Are There in Cladistics?

1. Change in characteristics occurs in lineages over time.2. Any group of organisms is related by descent from a common ancestor.3. There is a bifurcating, or branching, pattern of lineage-splitting. (when a lineage splits, it divides into exactly two groups)4. Changes occur in an orderly progression, i.e. ordered. (pg. 26 of J&C)5. Jumps between lineages (hybrids) aren’t easily dealt with6. If we assume “parsimony” we are sometimes fooled. 7. Reversals and Convergence (Homoplasy) difficult to deal with

Let’s Construct Our Own Phylogenetic Tree (Cladogram)

• Consider the following four plants that grow here locally in the Gila National Forest as representatives of their families:

• Urtica dioica (Stinging Nettle, Urticaceae)• Ceanothus greggii (Desert Buckthorn,

Rhamnaceae)• Morus microphylla (Littleleaf Mulberry, Moraceae)• Ulmus pumila (Siberian Elm, Ulmaceae)

Consider These Three Character States:

• Flower size: conspicuous, or inconspicuous• Stamens: >5 & straight, or <5 & incurved• Sap: Milky, or clear

Urtica dioica subsp. gracilis

Urtica dioica subsp. gracilis

Urtica dioica subsp. GracilisCharacter states

• Flower: inconspicuous• Stamens: 4, incurved• Sap: at least somewhat milky

Ceanothus greggii

Ceanothus greggiiCharacter states

• Flower: conspicuous• Stamens: 5, straight• Sap: clear

Morus microphylla

Morus microphyllaCharacter states

• Flower: inconspicuous• Stamens: 5, straight• Sap: milky

Ulmus pumila

Ulmus pumilaCharacter states

• Flower: inconspicuous• Stamens: 5, straight• Sap: clear

Construct a Matrix…

Flower Type Stamen Type Sap Type

Urtica gracilis

Ceanothus greggii

Morus microphylla

Ulmus pumila

Construct a Matrix

Flower type Stamen type Sap type

Urtica gracilis inconspicuous 4, incurved milky

Ceanothus greggii conspicuous 5, straight clear

Morus microphylla inconspicuous 5, straight milky

Ulmus pumila inconspicuous 5, straight clear

Make Your Network

Make Your Network

Ceanothus greggii Ulmus pumila Morus microphylla Urtica dioica

A B C D flower state type of sap stamens

conspicuous inconspicious clear milky >5, straight <5, incurved

What Do You Need to Root the Network?

• You need an outgroup• Outgroups are assumed to have separated from

the ingroup lineage before the ingroup diversified; i.e., the ingroup members are more closely related to each other than they are to the outgroup.

• The point at which the outgroup attaches to a network is therefore determined as the root of the tree.

Add the the Outgroup

• Let’s use Rosa woodsii as a representative of the Rosaceae as the outgroup.

• Here are the character states of Rosa woodsii: Flower: conspicuous Stamens: >5 Sap: clear Now– root your network by attaching Rosa woodsii at the most appropriate spot.

Congrats! Meet the Rosales!

Reading for Wednesday: Morphology of Vegetative Structures: Judd and Campbell pp. 53-61